The recently developed Model S1035 Advanced Crew Escape Suit (ACES) represents the latest generation pressure suit system developed for the NASA Space Shuttle program, and serves as a replacement for the S1032 Launch Entry Suit (LES).The S1032 Launch Entry Suit (LES) was developed following the Challenger loss and NASA's decision to integrate a Shuttle crew escape system. The development effort took advantage of previous pressure suit developments, with each major LES component being selected from previously qualified systems. The primary design challenge was one of design integration with the Orbiter and other crew escape equipment. The S1032 LES has successfully supported Shuttle missions since NASA's Return to Flight with STS-26 in September 1988.Initiated in 1990, the S1035 ACES was designed to be a simplified, lightweight, low bulk pressure suit which facilitated self donning/doffing, provided improved comfort and enhanced overall performance in order to reduce crew member stress and fatigue. Favorable crew member evaluations of a prototype led to full scale development and qualification of the S1035 ACES between 1990 and 1992. Production of the S1035 ACES commenced in February 1993, with the first unit being delivered to NASA in May 1994. The S1035 ACES first flew aboard STS-68 in August 1994 and will become the primary crew escape suit when the S1032 LES reaches the end of its service life beginning in late 1995.